What is shown in the diagram? a). a turbine b). an electromagnet c). a motor d). a generator

Explain why electric current cannot exist if a current doesn't have a voltage source.

Asolid cylinder and a cylindrical shell have the same mass, same radius, and turn on frictionless, horizontal axles. the cylindrical shell has light-weight spokes connecting the shell to the axle. a rope is wrapped around each cylinder and tied to blocks of equal masses that are held the same height above the ground. both blocks are released simultaneously. the ropes do not slip. which block hits the ground first? or is it a tie?

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion